The Power Grid
Comments for
Teachers
Lesson 1
The applet at http://tcip.mste.uiuc.edu/applet2.html provides a
simulation of a large scale power system network.
• The green arrows show the
Encourage students to explore the applet. Then use
the lessons on the student pages to focus their
explorations.
direction the power is
moving. The
There are more than 6000 utility scale
current is
generators in the U. S. They are powered by
Hydroelectric generators use differences
flowing out of burning coal, oil or natural gas, or by nuclear
in water elevations to drive turbines. One
famous example is the Hoover Dam.
fission,
falling
the
water or wind.
generators,
through the substations
and into the communities.
Bigger arrows indicate
more power.
• You can open or close the
blue switches by
Natural gas
clicking them
generators tend
with the mouse.
to be expensive
to operate, but
• There are five
Wind
they are capable
turbines
of changing their
generators
are clusoutput quickly.
represented in
tered
together
this simulation. The coal,
to make
hydropower and natural gas
wind
farms
generators
Coal generators are
capable
cheapest fossil
of
have adjustable the
based generators.
produThey can change
outputs. The
cing utility scale power levels. Their
their output a little less quickly than the
power output varies with wind speed
others do not. natural gas generators.
and often good wind sites are far
Nuclear
generators
are
Click on the up
from areas that need the most power,
powered by a uranium
so wind accounts for only a small
and down arrows to the
fission process. They
portion of generated power. The U.S.
Courtesy of DOE/NREL, Credit
are expensive to build,
right of MW output labels - Warren Gretz
Department of Energy proposes that
but inexpensive to
wind might supply 20% of the nations
operate. They provide
to change the production.
power by the year 2030.
large amounts of
All of the generators have
power.
blue connection switches.
Simulation Generators and their outputs
More Resources
• How Power Grids Work http://www.howstuffworks.com/power.htm
• The Power of the Wind http://www.mste.uiuc.edu/projects/wind
• The Magic School Bus and the Electric Field Trip by Joanna Cole.
Illustrated by Bruce Degen. Scholastic Press, New York. 1997.
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11/7/2008
◊ Wind, 200 MW, varies with wind speed
◊ Natural gas 0 MW - 500 MW,
adjustable
◊ Coal, 300 MW - 700 MW, adjustable
◊ Hydroelectric, 500 MW - 1000MW,
adjustable
◊ Nuclear, 900 MW, not adjustable
The Power Grid
Lesson 1
Use the applet at http://tcip.mste.uiuc.edu/
applet2.html to explore how power is distributed
from generators to the communities. In the applet
there are five different types of generators
delivering electricity to three communities. When
the applet opens, are the generators making more
or less power than the communities are using? ____
Some of the generators are able to vary their
production. Click on the up and down arrows to the
Courtesy of DOE/NREL, Credit - Warren Gretz
right of MW output labels to change
the production.
Find the five generators. List the types and
Read about
the power
grid here.
The power grid refers to
the system of producers
and consumers of
electricity. It includes power
generators, the users of electricity,
their outputs here. If a generator is able to vary
its output, give its range.
1.
2.
3.
switches that control the electricity,
4.
and the system of substations, power
5.
lines, and transformers that deliver
the electricity.
A community might have a generator
to provide its power. The generator
The arrows show the direction of the power flow and
indicate the amount. Open or close the blue switches by
clicking with the mouse. Explore the system by changing
the power outputs and opening or closing the switches.
may be able to vary its production as
When the applet opens (or is reset), power is being
the usage of the customers changes,
produced by four of the five generators.
but there may be times when the
Find the total amount of power being produced.
demand for energy is too great for
_______________ You can see the power moving
the generator. Then the community
from the generators through the substations and
buys electricity from another source.
to the users in Commerceton, Industryville, and
At other times
One estimate of home
energy use states 3.3 MW the generator
are needed for 1000 homes
may be making
Residenceburg. Find the total amount of power
being used by these communities. _________Any
power that is not used by the communities in the
more electricity than the community
system is sent to other users in other systems.
is using, so it wants to sell it.
How much power is being sent to external
systems? ___________
2
The Power Grid
Comments for
Teachers
Lesson 2
When the applet at http://tcip.mste.uiuc.edu/applet2.html opens,
power is being produced by four of the five generators. You can
see the power moving from the generators through the
substations and to the users in Commerceton, Industryville, and
Residenceburg. Any power that is not used by the communities in the system is sent to
users in other systems. If the generators in this system are not producing enough power,
power will be purchased from other systems. In the applet this is indicated by the two
External Systems. This simulation is designed to blackout if both External Systems are
disconnected from the system.
The sum of the power entering a substation must equal the sum of the power exiting that
substation. For example, when the applet starts (or is reset), the coal generator is sending
600 MW of power to Substation 3. Industryville is receiving 100 MW of that power and
500 MW is going to Substation 2.
Ideally, a local power system would generate exactly as
much power as it uses, but because power demand is
constantly changing, this is often not possible. There is
no easy or economical way to store large amounts of
electricity, so any “extra” power is sent to other users.
Generation systems, like the one in the applet, are
interconnected to allow electricity to travel. This
interconnected system is the power grid. There are
more than one hundred energy control centers across
North America. Here power system operators monitor
power production, transmission and use. They try to
make sure that power demand across the grid is equal to
power generated. They also try to keep costs low and
make sure equipment is operating safely. They may ask a
generator to produce more power or less at times.
When you are interacting with the applet, you are acting
like a power system operator.
More Resources
• The Midwest Independent Transmission System
Operator, Inc. in Indiana works to manage transmission for
an area from Ohio to Manitoba
http://www.midwestiso.org/home
• Take a virtual power plant tour at
http://www.energyclassroom.com/powersource.html.
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11/7/2008
McNeil Generating station control room
Courtesy of DOE/NREL
Lesson 2
The Power Grid
When the applet at http://tcip.mste.uiuc.edu/applet2.html opens (or is reset), power is being produced by four of the five generators. Close the switch to put the nuclear plant
online. What changes? ___________________________________
_____________________________________________________
_____________________________________________________
Now, how much power is being sent to external systems? __________
What happens if the switch to one of the external systems is opened?
Watch the arrows
and the numbers
alongside the
transmission lines to
see changes in
thesystem.
___________________________________________________________________
____________________________________________________________________
How can you match the power generated to the power used? ______________________
___________________________________________________________________
When do the arrows change direction? ______________________________________
Take all of the generators offline. What happens?
You see some parts of the power grid
_____________________________________
all around you. There is probably a
Put only the hydroelectric plant back online. Now
power pole with a transformer drum
what happens? __________________________
very near where you live. If your
neighborhood has underground power,
A power substation
Reset the system,
the transformer is in a green box
then answer these
that is about one meter on each side.
questions. Adjust the
There is a power substation like the
coal power plant to be
one in the photo nearby too.
Substations can split the power
distribution into two or more
directions, but they do not make or
use power. So the power entering a
substation is equal to the power
leaving the substation. Another job
on line at maximum
power. How much electricity is flowing into
substation 3? _______ How much electricity is
flowing out of substation 3? ________ Where is
it going?
_____________________________________
of the substation is to take the high
_____________________________________
voltage power produced by the
What changes when you open the switch on the line
generators and transform it to a
leaving the coal plant? _________________
lower voltage that can be used in
_____________________________________
homes, schools and businesses.
_____________________________________
4
The Power Grid
Comments for
Teachers
•
Lesson 3
The transmission lines in the applet have varying capacities.
They range from 1000 MW to 2000 MW. The line flow for each
line is noted near the line and changes as the power flow changes.
•
When a line is carrying less than 85% of its capacity, the arrows are green, indicating
that the flows are within normal operating conditions. As the flow moves past 85% of
the line capacity, the arrows turn
orange, indicating that the lines should
not be made to carry much more power.
As the flow continues to increase past
the maximum, the arrows turn red. If
the arrows remain red (i.e., the line
remains overloaded) for approximately
10 seconds, the line automatically opens
and a notification is displayed
•
If a community demands more power
than the transmission line that serves it
can carry, the community will blackout.
A community may also blackout if a line is damaged. In the applet as well as in reality,
a transmission line problem in one area of the system can cause blackouts in several
areas.
•
Power lines are designed with maximum capacities. The large diameter, more
expensive high voltage lines leaving a generating plant are designed to carry the
maximum that the plant can produce. It’s more difficult to design a transmission line
that supplies a community because growth and demand are harder to estimate.
More Resources
• Electric Power Generation, Transmission and Distribution: Illustrated Glossary (OSHA) http://
www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/index.html
• CBS News coverage of the power blackout in August, 2003 http://www.cbsnews.com/
stories/2003/08/14/national/main568370.shtml
• Energy Story, California Energy Commission http://www.energyquest.ca.gov/story/
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11/7/2008
The Power Grid
Lesson 3
When the applet at http://tcip.mste.uiuc.edu/applet2.html
Victoria Towers residents sit outside with their
flashlights during the power blackout Aug. 14, 2003,
in Meriden, Connecticut (Photo AP)
opens (or is reset), all of the power flow arrows are green.
The transmission lines have varying
capacities. Just as in an actual power system, if a line is asked to carry
too much power the line will be opened creating a power outage. To make
it easy for the system operator (that’s you!) to see when lines are in
danger of becoming overloaded, the arrows in the applet change color.
Reset the system and notice the line leading from Substation 5 to
Commerceton. How much power is this line carrying? _________ Click
on the up arrow to increase Commerceton’s power demand. What
happens to the arrows on the line? __________________________
At what load do the arrows change to orange? _______________ What color are the
arrows when the demand is 1000 MW? ___________________ What happens when the
load on the line is increased again? ________________________________________
How can you fix it? ___________________________________________________
Explore the applet to find the line maximum capacities for all the lines.
Power leaving the generating plant
Reset the system, put the nuclear power plant online
is carried by high voltage, long
and then increase the power demanded by
distance transmission lines to a
Residenceburg to 1850 MW. What’s causing a
distribution substation. These lines
problem? _______________________________
look like the photo. The power leaves
Reduce the potentially dangerous line overload
the substation on the lines you see
without taking the nuclear plant offline. How do you
strung from power poles. The
do this? ________________________________
transmission lines that have the largest
_______________________________________
diameters are designed to carry the
It’s a hot summer day and power demand in
most power. Transmission lines become
Residenceburg is 1600 MW. Commerceton is
hot and expand if they carry more
demanding 850 MW and Industryville needs 800 MW.
power than they are designed to carry.
You put all of your generators online at maximum
This can cause the line to sag and touch
capacity. Are all of your lines operating safely?
the ground or some other object.
_____ Are you able to produce enough power to
When this happens the line is opened
meet the demand or do you need to get power from
and a power outage will occur.
the external system? _______________________
6
The Power Grid
Lesson 4
Comments for
Teachers
This configuration of the applet at http://tcip.mste.uiuc.edu/
applet2.html shows Residenceburg and Commerceton demanding
power that is near the maximum transmission capacity of the
power lines that supply their
communities. The generators
in the system are able to
provide the demanded power
with very little demand on
the external systems, but if
either or both of these
communities demand much
more power the transmission
line supplying it may open and
blackout the community. The
high demand from these
communities also puts a high
load on lines elsewhere in the
system. This is an example
of how a problem is one part
of the power grid can
become a massive outage.
Discuss with students the benefits of combining local generation with the external
system to allow for changing demands from users. While the interconnected grid allows
for more efficient use of generated power, there is always
the danger of a problem in one part of the grid affecting
large areas of the system. Power engineers and others in
the power industry are working to find ways to maximize
the reliability of the power grid.
Courtesy of DOE/NREL, Credit -
More Resources
Linenberger, Mike
• The Federal Energy Regulatory Commission is responsible for the reliability of high
voltage transmission between states. http://www.ferc.gov/about/ferc-does.asp
• AREVA has some animations and videos of their operations at http://www.areva.com/
servlet/understand/ouroperations-en.html
• Energyville is an energy game sponsored by Chevron Corporation. http://
willyoujoinus.com/energyville
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11/7/2008
The Power Grid
Lesson 4
When the applet at http://tcip.mste.uiuc.edu/applet2.html opens (or is reset), the
generators are producing more power than the communities are using, and power is being
sent to the external system. Power system operators try to match power generation to
demand, because this is the least expensive. When communities need more power, the
generators are adjusted. The transmission line
flows need to be kept at safe levels too.
Reset the system and then set the power demand
for Residenceburg at 1500 MW, for Industryville
at 600 MW and for Commerceton at 800 MW.
Turn the nuclear power plant on to meet this
increased demand.
Bad weather can sometimes cause breaks in
transmission lines. What happens to the system
Courtesy of DOE/NREL, Credit - Kelly, Marguerite
when you open the line between substations 4 and 6? ___________________________
___________________________________________________________________
___________________________________________________________________
Reset the system, turn on the nuclear power plant and then open the line between
substations 1 and 2. What happens? _______________________________________
___________________________________________________________________
What is the problem? ___________________________ Fix it by changing one switch.
What did you do?______________________________________________________
There are six major Regional Transmission
Organizations (RTO’s) or Independent
System Operators (ISO’s) in the United
States. These voluntary, independent
Reset the system and then set both the coal
generator and Industryville to 600 MW. What
is happening between substations 2 and 3?
____________________________________
organizations monitor electricity
____________________________________
generation and demand and communicate
Open the line between substations 2 and 3. Now
with power plants and utilities to balance
what is happening? ______________________
supply and demand. The Federal Energy
What happens to the other communities?
Regulatory Commission (FERC) encourages
___________________________________
the formation of these nonprofit
organizations because they promote
efficiency in wholesale electricity markets.
Which line is this system do you think is most
likely to overload? ______________________
____________________________________
8
TCIP is funded by:
The National Science Foundation
The Department of Energy
The Department of Homeland Security
http://tcip.iti.uiuc.edu
TCIP Educational Development is a
joint project of the Office for
Mathematics, Science and
Technology and Information Trust
Institute at the University of
Illinois.
These materials were developed by
Jana Sebestik and Zeb Tate in
consultation with George Reese and
Molly Tracy
http://tcip.mste.uiuc.edu/
For More Information:
Information Trust Institute
University of Illinois at Urbana-Champaign
450 Coordinated Science Laboratory
1308 West Main Street, MC-228
Urbana, IL 61801
217.333.3546
info@iti.uiuc.edu
http://www.iti.uiuc.edu